Battery cells may be used as energy sources for mobile devices, electric vehicles, hybrid vehicles, and the like. The shape of the battery cell may be variously changed depending on the kind of external device to which the battery cell is applied.
A small-sized mobile device such as a cellular phone may be operated with the power and capacity of a single battery cell for a certain period of time. In contrast, to increase power and capacity, a large capacity battery module having longer driving times, higher driving power, and/or larger power production capabilities may be used for an electric vehicle, hybrid vehicle, and the like, which has large power consumption. The battery module increases output voltage or current according the number of battery cells built therein. A battery pack may be configured by electrically connecting a plurality of battery modules.